(a) Field of the Invention
The present invention relates to a thin film transistor array panel and a manufacturing method thereof.
(b) Description of the Related Art
Generally, a thin film transistor is used as a switching element for independently driving each pixel in a flat panel display, such as a liquid crystal display and an organic light emitting display device. A thin film transistor array panel including the thin film transistors has scanning signal lines (or gate lines) for transmitting scanning signals to the thin film transistors, and data lines for transmitting data signals to the thin film transistors, as well as pixel electrodes connected to the thin film transistors.
Each thin film transistor includes a gate electrode connected to a gate line, a source electrode connected to a data line, a drain electrode connected to a pixel electrode and a source electrode, and a channel layer formed on the gate electrode between the source electrode and the drain electrode, and transmits a data signal from the data line to the pixel electrode according to the scanning signal from the gate line.
Here, the channel layer of the thin film transistor is preferably made of polysilicon (polycrystalline silicon, polysilicon), amorphous silicon, or an oxide semiconductor.
Recently, research of an oxide semiconductor has been actively developed. The oxide semiconductor may be deposited at room temperature, and has good uniformity in comparison with polysilicon and higher current mobility in comparison with amorphous silicon.
When forming the thin film transistor semiconductor with a bottom gate structure using the oxide semiconductor, the oxide semiconductor may be exposed to the atmosphere and the channel portion of the oxide semiconductor may be damaged by vapor or by the dry etch gas when etching a metal layer formed on the oxide semiconductor, and accordingly the characteristics of the thin film transistor may be seriously degraded. Furthermore, to prevent damage by the dry etching as above described, a wet etching method may be used. However, it is difficult to form the thin film transistor when the etching speed for the oxide semiconductor is higher than that of the upper metal layer.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.